Gai’s children — both with twisted limbs and confined to wheelchairs — were born in a village that was drenched with Agent Orange during the Vietnam War. She believes their health problems were caused by dioxin, a highly toxic chemical in the herbicide, which U.S. troops used to strip communist forces of ground cover and food.

Thirty-five years after the end of the Vietnam War, its most contentious remaining legacy is Agent Orange. Eighty-two percent of Vietnamese surveyed in a recent Associated Press-GfK Poll said the United States should be doing more to help people suffering from illnesses associated with the herbicide, including children born with birth defects.

After President George W. Bush pledged to work on the issue on a Hanoi visit in 2006, the U.S. Congress has approved $9 million mostly to address environmental cleanup of Agent Orange. But while the U.S. has provided assistance to Vietnamese with disabilities — regardless of their cause — it maintains that there is no clear link between Agent Orange and health problems.

Vietnamese officials say the U.S. needs to make a much bigger financial commitment — $6 million has been allocated so far — to adequately address the environmental and health problems unleashed by Agent Orange.

“Six million dollars is nothing compared to the consequences left behind by Agent Orange,” said Le Ke Son, deputy general administrator of Vietnam’s Environmental Administration. “How much does one Tomahawk missile cost?”

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Tran Van Tram and Tran Thi Dan are desperate for help. Their four grown children crawl around the family home on all fours, rumps in the air. They have trouble standing up straight and can take no more than a few steps at a time with a walker.

Each of his children appeared healthy at birth, said Tram, 61. But after a year or so, they could not roll over. They never learned to talk.

Tram remembers watching U.S. planes dump Agent Orange several times daily over his village in Quang Tri Province, near the former demilitarized zone that once divided North Vietnam and South Vietnam. He used to fish in nearby lakes and streams every day.

Now he and his aging wife spend virtually all their time caring for the children.

They shower the children outdoors, an ordeal for all concerned. Hoang, 26, sat on the patio recently after his father hosed him down, and waited for his mother to pull his pants on. His spine is bent and he has a large lump on his back.

“I have no time for myself,” said Dan, 59. “Even when I die, I will have no peace. I will always be worried about my children. Who will take care of them when we are gone?”

Dan says she can’t believe it’s a coincidence that many of her neighbors started having children with birth defects after the war ended.

“It’s not just my family,” she said. “Many families here are suffering the same problems. I’d like to see the United States government do more to help ease the pain of the war.”

Between 1962 and 1971, the U.S. military sprayed roughly 11 million gallons of Agent Orange across large swaths of southern Vietnam. Dioxin stays in soil and the sediment at the bottom of lakes and rivers for generations. It can enter the food supply through the fat of fish and other animals.

Vietnam says as many as 4 million of its citizens were exposed to the herbicide and as many as 3 million have suffered illnesses caused by it — including the children of people who were exposed during the war.

The U.S. government says the actual number of people affected is much lower and that Vietnamese are too quick to blame Agent Orange for birth defects that can be caused by malnutrition or other environmental factors.

“Scientists around the world have done a lot of research on dioxin and its possible health effects,” said Michael Michalak, the U.S. ambassador in Hanoi. “There is disagreement as to what’s real and what isn’t, about what the possible connections are.”

That position frustrates many Vietnamese, who point out that the U.S. government banned commercial use of the herbicide long ago and provides benefits to American veterans who were exposed to Agent Orange while serving in Vietnam.

The U.S. Veterans Administration covers the medical treatment of American servicemen who were exposed to Agent Orange and subsequently developed one of 17 illnesses associated with dioxin. Children of exposed servicemen who were born with spina bifida also receive a medical benefit.

“American and Vietnamese Agent Orange victims haven’t been treated the same way, and it’s not fair,” said Tran Xuan Thu, secretary general of the Vietnam Agent Orange Victims Association, whose suit against the U.S. manufacturers of Agent Orange in 2005 was rejected by a U.S. court. “It’s not in keeping with the humanitarian traditions of the United States. I hope the American people will raise their voices and ask their government and the chemical companies to take responsibility.”

U.S. officials point out that an “association” has been established between Agent Orange and the illnesses on the list, but that the scientific evidence has not been high enough to establish a causal relationship.

“We don’t know if there’s any linkage or not, but we believe in trying to do our best to take care of our veterans,” Michalak said. “If Vietnam wants to take care of its veterans, then we think that is a very worthy cause.”

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The U.S. spends just a small sliver of its budget in Vietnam on Agent Orange. Last year, it allocated more than $80 million for the fight against HIV/AIDS in Vietnam, where the epidemic is relatively mild, but just $3 million for Agent Orange work.

A coalition of non-profit groups led by the Ford Foundation, which has been trying to draw attention to the herbicide’s toxic legacy, spent more than the U.S. government.

Tests conducted by Hatfield Associates, a Canadian environmental firm, have shown that dioxin is within safe levels across most of Vietnam. But it is well beyond acceptable levels at a number of “hotspots” where U.S. soldiers used to mix, store and load Agent Orange onto planes.

According to one estimate, cleaning up the three biggest hotspots — at former airbases in Danang, Phu Cat and Bien Hoa — could cost as much as $40 million.

Since 2006, at the request of the Vietnamese government, the United States has been focusing its Agent Orange work on Danang. Tests taken by Hatfield found extremely high levels of dioxin — up to 400 times accepted international limits — in soil samples taken near the site and in the blood of a few dozen people who lived near a contaminated lake on the old airbase, where they often went fishing.

Working with Vietnamese officials, the U.S. government has sealed off the site to prevent further leakage of dioxin. They are now seeking ways to decontaminate the site, which is likely to cost millions of dollars.

More than two-thirds of the U.S. money allocated so far has been devoted to cleaning up the Danang hotspot, with just $2 million set aside for health programs to serve disabled people in the area.

Since 1989, Michalak said, the United States has spent $46 million to help Vietnamese with disabilities, but it does not keep track of how many of the beneficiaries have illnesses associated with Agent Orange.

“We just think it’s the humanitarian thing to do, it’s the right thing, and it helps to improve relations between the two countries,” Michalak said.

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The current U.S.-Vietnam efforts to enhance cooperation on the issue stand in marked contrast to their disagreements seven years ago, when the two sides attempted to conduct a study of birth defects in children whose mothers were exposed to Agent Orange.

The study fell apart amid bickering and finger-pointing. When the Vietnamese and American scientists failed to agree on how to design the $1 million project, the U.S. National Institute on Environmental and Health Sciences withdrew funding.

A leaked U.S. embassy memo written in 2003 captures the bitterness and suspicion that divided the two sides.

Vietnam’s claims about Agent Orange were “grossly exaggerated and unsupported by any objective measure,” the memo said, dismissing Vietnam’s concerns as a “propaganda campaign” to morally indict the U.S. government and win financial compensation.

The memo, circulated in Hanoi by a former embassy staffer, was omitted from more than 100 pages of State Department documents released to The Associated Press in response to a Freedom of Information Act request last year. Those documents, which were heavily edited, also show that the U.S. was deeply skeptical of Vietnam’s assertions about Agent Orange.

The U.S. has shifted its tone sharply since the 2003 memo, but it has not changed its basic position: current science does not support Vietnamese claims about Agent Orange. No exhaustive studies have been done in Vietnam, where available records on birth defects are incomplete, U.S. officials say, making comparisons of populations difficult.

Vietnam says its own studies show that the rate of birth defects in areas sprayed with Agent Orange is four times higher than in areas that weren’t sprayed, and the incidence of certain cancers was 10 times as high.

Le Ke Son, one of Vietnam’s top environmental officials, said countries around the world have concluded that dioxin is one the most toxic chemicals on earth.

“Not one of them would say dioxin is not harmful to people,” Son said.

David Carpenter, the U.S. scientist who won funding for the ill-fated 2003 study, agreed with that assessment. He planned to test 800 Vietnamese children to see if Agent Orange exposure in mothers increased their chances of being born with one of three kinds of birth defects.

Many of the birth defects Vietnamese have attributed to Agent Orange may have other causes, Carpenter said, but there is little doubt that the herbicide is to blame for some.

“Dioxin is just a horrible chemical,” Carpenter said. “There are a variety of factors that contribute to birth defects, and dioxin is certainly one of them. One need not be a rocket scientist to come to that conclusion.”

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Gai and her husband, Nguyen Van Bong, remember watching American planes dump their poisonous cargo on the jungles near their home in Cam Tuyen, where they scratch out a living from their tiny family farm.

“We used to see white clouds coming from the planes,” Bong said. “We ate fish and drank water from nearby rivers and streams.”

The couple is convinced that dioxin is to blame for the fact that their two daughters now have curved limbs, spines and fingers. Thuyet, 16, shrieks day and night, her screams reverberating through the family’s two-room home.

“I barely sleep at night,” Gai said. “I have to keep an eye on them all the time.”

The girls are usually up by 3 a.m., when Gai boils water to bathe them.

Then the 51-year-old mother dresses her daughters and lifts them into wheelchairs. They watch while she washes their clothes in a stream.

Three times a day, she performs physical therapy on the girls for 20 minutes, stretching and massaging their misshapen limbs to ease their pain.

“If I don’t do the therapy, Thuyet would scream even more,” Gai said. “I sing to them each time before I massage them. It calms them.”

Once a month, a village volunteer comes to help for a half hour. Other than that, Gai and Bong are on their own.